Growing up in a “non-denominational”, independent fundamental Baptist house I was always taught that Catholics weren’t Christians because they worship idols. Now that I’ve left the faith I would easily classify them as being Christian.

While I think many people actually do classify them as Christians they do have some significant differences in their beliefs and practices than most Protestant denominations; and being themselves the largest Christian denomination by far it can be useful in some analysis to treat them as a distinct entity (the answer to “percentage of global population that subscribe to a particular religion” is much more interesting when broken into “Christian Catholic: %” and “Christian Other: %”).

It’s because Protestantism is the dominant form of Christianity in cultures where this language convention exists, and it is a deliberate tactic to other Catholics by labeling them non-Christian. Especially in previous times, Catholics were subject to large amounts of discrimination and antagonism by Protestants, and we’re still dealing with the remnants of this ideology today. I think the only reason it has subsided is the rise of secularism and other more foreign religions that are seen as a greater threat by Christians, forcing them into an uneasy alliance with their former enemies. But remember that tons of Christians used to murder each other over which sect they belonged to.

Interestingly, in Central America, the opposite convention exists, where you are either “Cristiano”, meaning Catholic, or “Evangelico”, meaning Protestant (usually Pentecostal). This is because the dominant group is reversed in that society.

Personally, I view Christianity, Islam, and Judaism as three branches of one religion since they are clearly very similar. But that is the view of an outsider.

Because some sects of Christianity (mostly Southern Baptist) are fucking insane and spiteful.

I can maybe understand it if they’re talking about UUs. Speaking as one, we’re not entirely sure what the hell we are either. We’re in committee trying to figure that out.

Hundreds of years of infighting

This might be a regional thing. At least in Germany, where the reformation took place, the term Christian include all groups, protestans, catholics, orthodox etc.

some sort of remnant of evangelical puritan protestant ideology?

Yes. It’s weird.

Catholics see themselves as the root form of Christianity that other versions forked from. Whilst it’s not technically true, as there are many versions of Christianity that pre-date Catholicism, in most countries where the term “Catholics and Christians” is used, it’s accurate enough

I’ve never heard someone say this.

As an American who was raised Lutheran, who was taught a bunch of Romance-Euro-centric world history in school, I always considered Roman Catholic to be the “default” flavor of Christianity. Protestantism in all of its forms are hard forks. It’s in the name, even–the Roman Catholic church is what Protestants are “protesting”.

To unironically “-and Zoidberg” Catholicism out of Christianity while leaving Protestant flavors included feels completely backwards. I’ve never heard anyone do it.

But if I did, I could only assume it was due to some No True Scotsman bullshit. “Only we practice the correct way. Everyone else isn’t just interpreting it differently, but interpreting it wrong.” Sounds like an Evangelical line of thought to me.

Discrimination and division are like 99% of what religion is about.

They have the next outgroup to eliminate lined up in case they run out of minorities to discriminate against.

Catholics are Christians, but Christians are not necessarily Catholic. For example, Orthodox Christians are not Catholic. Being Catholic requires, at the bare minimum, agreement with the Holy See and implicitly the dogma he endorses. Even this “minor” difference can be used to find non-Catholic Christians.

Precisely, Catholic ⊊ Christian.

The reason why this is the case has to do with the history of Christianity, specifically the various schisms throughout the ages as the Christian faith evolved. That’s an incredibly complicated topic which I’m not qualified to discuss.

If you believe your religion is the only correct one, you’ll make sure to distance yourself from other variants even of the same faith.

America is far from Europe and if there are people believing the US is the pinnacle of creation and Trump reincarnated Jesus himself, that phrase will eventually come up and stick

because historically lumping protestants and catholics together has not ended well.

Schism was the very first thing the Christian church learned to do.